Cabin doors for entering the passenger cabin of an aircraft are usually kept small deliberately, in order not to weaken the support structure of the aircraft made up of the fuselage skeleton and outer skin more than necessary as a result of the door opening for the cabin door. The larger the discontinuity in the outer skin as a result of the door opening, the larger is the loss of stability of the support structure in the area of the cabin door. In order to keep the loss of stability as small as possible, therefore, the cabin doors are deliberately kept small, as already mentioned, and are located in the area of a frame or rib, which however is interrupted at the place at which the door opening should be located. In order to compensate for this loss of stability, accordingly the respective adjacent ribs are formed in a reinforced manner. Based on this arrangement between two ribs, cabin doors today are very narrow, which during boarding may lead to accumulation and holdup of passengers at the cabin doors, who would like to enter the aircraft as quickly as possible.